Ankle replacement system

ABSTRACT

A total ankle replacement system, novel surgical method for total ankle replacement, and novel surgical tools for performing the surgical method are described. The total ankle replacement system includes the calcaneus in fixation of a lower prosthesis body, thereby significantly increasing the amount of bone available for fixation of the lower prosthesis body and allowing the lower prosthesis body to be anchored with screws. The total ankle replacement system further includes a long tibial stem which can also be anchored into the tibia with, for example, screws, nails, anchors, or some other means of attachment. The novel surgical arthroscopic method allows introduction of ankle prostheses into the ankle joint through an exposure in the tibial tubercle. Various novel surgical instruments, such as a telescoping articulating reamer and a talo-calcaneal jig, which facilitate the novel surgical method, are also described.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/700,283, filed Nov. 3, 2003, now U.S. Pat. No. 6,860,902, which is adivisional of U.S. patent application Ser. No. 09/694,100 filed 20 Oct.2000, now U.S. Pat. No. 6,663,669, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/160,892, filed Oct. 22, 1999,and entitled “Ankle Replacement Systems,” all of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to ankle replacement systems including designs,methods and apparatus that reduce and/or prevent problems associatedwith subsidence, loosening, and late infection, in part, byincorporating a novel surgical procedure for replacing an ankle, atleast in part, through a tibial tubercle exposure. The present inventionis also directed to novel surgical instruments useful for performing anankle replacement procedure.

2. Description of the Background

Until the early to mid 1970's, patients with injured or diseased anklejoints commonly resulting from rheumatism, or degenerative or traumaticarthritis, had few options when their ankle joints failed. The mostcommon procedure to help these patients regain some use of their anklewas obliteration of the joint by fusion, a procedure that is stillcommonly used today. Fusion, however, rendered the ankle stiff andgenerally immobile relative to the lower leg, resulting in limited useand additional stresses on the knee and hip joints.

Probably the first reported use of total ankle prosthesis was byBuckholz in 1969. The medical community recognized that such anklereplacement led to largely increased use of the ankle joint because thereplacement permitted ankle ranges of motion which generally attemptedto mimic the natural human joint. Since that time, ankle replacementprostheses have become increasingly common in use and improved indesign.

An early ankle replacement prosthesis, disclosed in U.S. Pat. No.3,886,599, incorporated herein by reference, consisted of an articulatedtwo-part prosthesis having a convex-to-convex bearing surface providedby an upper metallic portion and a lower portion formed of high densitypolyethylene. The upper metallic portion had a stem adapted forengagement with a prepared distal end of the tibia, and the lowerportion had a shank adapted for engagement with and connection to aprepared surface of the talus.

Another early ankle replacement prosthesis, disclosed in U.S. Pat. No.4,069,518, incorporated herein by reference, comprised a talar memberwith three adjacent longitudinally and laterally convexly shaped bearingsurfaces with a means for attaching the talar member to the talus; and atibial member with three complementary longitudinally and laterallyconcavely shaped bearing surfaces with a means for attaching the tibialmember to the tibia.

Although these types of ankle replacements had some initial success inhelping patients regain use of their ankle joint, the long rangeprognosis for patients has not been good. For example, by the mid1980's, long term follow-ups were reported for patients who had receivedthese types of ankle replacements in the early to mid 1970's. At afollow-up of five years, failure rates were reported to be from 35% to76% in ankle arthroplasties. Failures have been found in all models oftotal ankle replacement including the Mayo Clinic Total Ankle, theOregon, and the Beck-Steffee models. See Kitaoka, H. B. et al., ClinicalResults of the Mayo Total Ankle Arthroplasty, J. Bone Joint Surg. Am.,1996; see also Wynn, A. H. et al., Long-term follow-up of the Conaxial(Beck-Steffee) Total Ankle Arthroplasty, Foot Ankle, 1992. Complicationsincluded aseptic loosening, delayed wound healing, wound dehiscence, andprosthetic subsidence.

Another ankle replacement device was described in a similar time periodin U.S. Pat. No. 4,232,404, incorporated herein by reference. Thisprosthesis comprises a talar component with a convex articulatorysurface that has an intermediate part-circular-cylindrical areacoaxially flanked at each end by similar mutually divergent part-conicalareas. The prosthesis also has a tibial component with an asymmetricalconcave articulatory surface complimentary with the convex cylindricalarea and one of the conical areas of the talar component. Additionally,this device has a fibular component which has an articulatory surfaceengaged with the other conical areas.

A similar device with tibial, fibular, and talar members has been in usesince 1984 under the name AGILITY™ Ankle by DePuy of Warsaw, Ind. In1997, outcomes of the first 100 total ankle arthroplasties using theAGILITY™ Ankle were reported by Dr. Frank G. Alvine, who had performedall 100 surgeries between 1984 and 1993. Approximately 61% of thereplacements were reported as successful syndesmosis fusions, while theremaining cases evidenced various problems from delayed unions andnonunions which were often associated with the development of ballooningand circumferential lysis at the tibial component. See OrthopaedicsToday, Jul. 7, 1997, pp. 16-17. The AGILITY™ Ankle takes advantage oftibiofibular sydesmosis for increased contact and better forcedistribution than the previous ankle replacements that relied onstability from connections to the talus and tibia. However, thetibiofibular syndesmosis is a large contributing factor in loosening andballooning osteolysis problems encountered with the AGILITY™ Ankle.

A more current ankle replacement device is described in U.S. Pat. No.5,766,259, incorporated herein by reference. This prosthesis alsocomprises tibial, talar, and fibular components. A floating bearing islocated between the tibial and talar prosthesis components. The floatingbearing makes full contact with the talar component and is capable oflimited medial-lateral and fore and aft movement with the tibialcomponent. The fibular component has a plastic insert which cooperateswith the talar and tibial components to provide stability to the anklejoint.

A common element between the previous ankle replacement systems, theAGILITY™ Ankle and the system described in U.S. Pat. No. 5,766,259 isthat they all comprise a talar member, fixed to the talus, as one oftheir main functioning components. The talus, however, is relativelysmall, providing a small area of bone for fixation. Also, in most ofthese ankle replacement systems, the talar component is cemented to thetalus. The combination of fixation with bone cement to a small fixationarea allows for erosion of the cement from the fixation area and anincrease in compliance due to formation of a soft tissue capsule overtime. This contributes to aseptic loosening and migration of the device.Furthermore, although more recent replacements have attempted toalleviate stress from the tibia and talus by incorporating a fibularcomponent and infusing tibiofibular syndesmosis, they still face commonproblems of prosthesis migration and loosening, and osteolysis at thetibial component.

Another common element between these previous systems is that they areinstalled through incisions made at or near the ankle. Such surgicalprocedures require making large incisions at the ankle, moving thetendons and other soft tissue aside, and separating the tibia and fibulafrom the talus—essentially detaching the foot from the leg—to installthe device, subsequently requiring complicated realignment andreattachment of the foot. In addition, these devices typicallyincorporate a relatively short tibial component to simplifyinstallation. These procedures commonly result in infection and extendedhealing time with possible replacement failure from improperrealignment. The surgery also has increased risks associated withcutting or damaging neighboring nerves and tendons which may lead tofurther complications.

There is, therefore, a need in the field for a total ankle replacementsystem that reduces the occurrence of subsidence and aseptic looseningwhile retaining the majority of the foot's natural motion. There is alsoa need for a less invasive surgical method to install such a device toprovide improved healing and a decreased failure rate.

SUMMARY OF THE INVENTION

The present invention overcomes the problems and disadvantagesassociated with current strategies and systems in total anklereplacement (TAR). In particular, the present inventive anklereplacement method and system is designed to prevent subsidence andaseptic loosening, problems common to the TAR devices currently in use.This device allows fixation of the lower prosthesis body to thecalcaneus and/or the talus, thereby significantly increasing the boneavailable for fixation. The enlarged available bone base allows fixationof larger trays and prosthetic bases and allows for anchoring of thelower prosthesis body with screws or other fixation methods not possiblewith fixation to only the talus. This prosthesis system provides greaterstability and stress absorption for the prosthetic ankle joint, anddecreases the probability of prosthesis loosening and subsidence.

In one embodiment, the novel ankle replacement prosthesis comprises amember that is attached to the calcaneus. In another embodiment, thenovel ankle replacement prosthesis comprises a lower member which isattached to both the talus and calcaneus in such a way as to fuse thetalus to the calcaneus. In yet another embodiment, the novel anklereplacement prosthesis comprises a lower member that is attached to boththe talus and the calcaneus, but which allows some relative movementbetween the talus and calcaneus, thereby closely mimicking the naturalmovement of the human foot. Said lower member could comprise a stemwhich incorporates a joint allowing relative movement between the talusand the calcaneus in a side-to-side manner. In a further embodiment, thelower member comprises a bony in-growth stem. The bony in-growth stemmay be about 45 to 75 mm in length and 7 to 15 mm wide and may beinstalled in a preformed cavity in the bone that exists from the top ofthe talus to the distal calcaneus. In yet another embodiment, the bonyin-growth stem is secured into the bone, for example, by screws, nails,anchors, or some other means of attachment.

In a further embodiment, the novel ankle replacement system comprises anupper prosthesis body. The upper prosthesis body comprises a tibialprosthesis which further comprises a long stem, approximately 150 mm inlength, preferably made of metal. In one embodiment, the long metal stemis covered with bony in-growth scintering.

The present invention also relates a novel surgical procedure forperforming TAR which reduces healing time and probability of infection,problems which contribute to the failure rate of currently available TARsystems. The novel surgical procedure comprises introducing ankleprostheses for TAR through the tibia into the ankle. In one embodiment,an exposure is made at the tibial tubercle with an awl. The tibia andtibial plafond are reamed with a tibial reamer inserted through thetibial tubercle exposure. Bony cuts are made in the talus and the end ofthe tibia. A hole is drilled from the talus into the posterior sectionof the calcaneus using a talar stem jig. After cartilage has beenscraped from the talo-calcaneal joint, a talo-calcaneal bony in-growthmetal stem is installed into the drill hole. A talar tray and a plasticdome are placed over the Morse taper on the talo-calcaneal stem and thetalar tray is fixed to the talus and calcaneus. A concave tibial dome isplaced in the ankle joint. A tibial stem is passed down the tibia to theankle joint. The end of the tibial stem is locked into the tibialcomponent and the stem is fixed into the tibia with, for example,screws. As part of this procedure, if desired, additional incisions maybe made in the foot and/or ankle to allow access to the joint and/orbones of the foot.

In a further embodiment, the top of the talus and end of the tibia maybe reamed with a reamer fitted over the end of a rotating shaft whichpasses through the tibia instead of, or in addition to, cutting thebone. In another embodiment, the metal talar tray may be fixed to thetalus and calcaneus with screws. In yet another embodiment, the tibialstem may be fixed to the tibia with screws.

Other objects, advantages, and embodiments of the invention are setforth in part in the description which follows, and in part, will beobvious from this description, or may be learned from the practice ofthe invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral view of the subtalar joint depicting talo-calcanealstem which has been installed into a preformed cavity in the talus andcalcaneus.

FIG. 2 is a lateral view of the foot and ankle depicting one embodimentof a TAR system of the present invention.

FIG. 3 is a lateral/skewed top view of the TAR system embodiment of FIG.2.

FIG. 4 is a posterior view of one embodiment of an installed TAR systemof the present invention.

FIG. 5 is a view of the human leg depicting a tibial tubercle exposure.

FIG. 6 is a lateral view of the human leg depicting a passed tibial rodadapted to hold an articular reamer.

FIG. 6 a is a bottom of an articular reamer.

FIG. 6 b is a top view of an articular reamer, showing the attachmentmember that allows the articular reamer to be attached to the distal endof a tibial reamer.

FIG. 7 is a lateral view of the subtalar joint being drilled to form ahole for a bony in-growth stem.

FIG. 7A is a top plan view of the talo-calcaneal jig of FIG. 7.

FIG. 7B is a cross-sectional view of the talo-calcaneal jig of FIG. 7A,taken along lines 7B-7B.

FIG. 8 is a side view of one embodiment of a lower prosthesis bodyconstructed in accordance with the teachings of the present invention.

FIG. 9 is a rear view of the lower prosthesis body of FIG. 8.

DESCRIPTION OF THE INVENTION System

As embodied and broadly described herein, the present invention isdirected to a novel system and method for Total Ankle Replacement (TAR).The ankle replacement system of the present invention includes a lowerprosthesis body desirably fixed to the calcaneus and/or the talus, whichgreatly increases the amount of bone available for fixation as comparedwith conventional TAR systems, which traditionally included only thetalus in fixation of a lower prosthesis. The enlarged available bonebase allows fixation of larger talar trays or other prosthetic bases toprovide greater prosthesis stability, and allows for anchoring of thelower prosthesis body with, for example, screws. This design providesgreater stability and stress absorption for the prosthetic ankle joint,and decreases the probability of prosthesis loosening and subsidence.

In one embodiment of the present invention, the subtalar joint is fusedto allow fixation of the lower prosthesis body to both the talus andcalcaneus. The subtalar joint may be fused using any method common tothose of skill in the surgical arts including, but not limited to,fusion with poly(methylmethacrylate) bone cement, hydroxyapatite, aground bone and marrow composition, plates and screws, or a combinationthereof. In the preferred embodiment, as depicted in FIG. 1 and FIG. 2,the talus and calcaneus are fused together with a talo-calcaneal stem110.

The talo-calcaneal stem 110 may be made of various materials commonlyused in the prosthetic arts including, but not limited to, titanium,titanium alloys, tantalum, chrome cobalt, surgical steel, or any othertotal joint replacement metal and/or ceramic, bony in-growth surface,sintered glass, artificial bone, any uncemented metal or ceramicsurface, or a combination thereof. The talo-calcaneal stem may furtherbe covered with various coatings such as antimicrobial, antithrombotic,and osteoinductive agents, or a combination thereof. These agents mayfurther be carried in a biodegradable carrier material with which thepores of the surface of the talo-calcaneal stem 110 may be impregnated.See U.S. Pat. No. 5,947, 893, which is incorporated herein by reference.If desired, the talo-calcaneal stem may be coated and/or formed from amaterial allowing bony ingrowth, such as a porous mesh, hydroxyapetite,or other porous surface.

The talo-calcaneal stem 110 may be any size or shape deemed appropriateto fuse the subtalar joint 90 of a patient and is desirably selected bythe physician taking into account the morphology and geometry of thesite to be treated. The physician is desirably able to select thedesired size and/or shape based upon prior analysis of the morphology ofthe target bone(s) using, for example, plain film x-ray, fluoroscopicx-ray, or MRI or CT scanning. The size and/or shape is selected tooptimize support and/or bonding of the stem to the surrounding bone(s).The stem 110 may be variable lengths from 2 cm to 12 cm and variablewidths from 4 to 14 mm. In the preferred embodiment, the talo-calcanealstem 110 is approximately 65 to 75 mm in length and approximately 7 to10 mm wide. While in the disclosed embodiment the stem has a circularcross-section, it should be understood that the stem could formed invarious other cross-sectional geometries, including, but not limited to,elliptical, polygonal, irregular, or some combination thereof. Inaddition, the stem could be arced to reduce and/or prevent rotation, andcould be of constant or varying cross-sectional widths.

The talo-calcaneal stem 110 is passed from the top of the talus into thedistal calcaneus, preferably through a cavity that has been drilledthrough the talus and calcaneus for fixation of the talo-calcaneal stem110. The talo-calcaneal stem 110 or a bone jig may be further adapted sothat the talo-calcaneal stem 110 is inserted as the cavity is beingdrilled or so that the talo-calcaneal stem itself is used to drill thehole. Moreover, if desired the stem could incorporate screw holes orother openings to accommodate interlocking hardware, such as screws, toincrease fixation and minimize rotation.

The talo-calcaneal stem 110 may additionally have interlockingcomponents, at its top surface to allow other components of thetalo-calcaneal prosthesis to lock and/or fit into the talo-calcanealstem. In the preferred embodiment, the talo-calcaneal stem 110, has aMorse taper 115 a at its upper talar end.

In one embodiment, a tray 130 is fixed to the top of the talus. Inanother embodiment a tray, any prosthetic base, or any lower prosthesisbody may be fixed or anchored to a fused subtalar joint, or to thecalcaneus only, or to both the talus and calcaneus in an unfusedsubtalar joint. In the preferred embodiment as depicted in FIG. 2 andFIG. 3, the tray 130 has an overhang portion 131 which allows the tray130 to overlap both the talus 100 and part of the calcaneus 105. Thetray 130 and overhang portion 131 may be made of various materialscommonly used in the prosthetic arts including, but not limited to,polyethylene, biologic type polymers, hydroxyapetite, rubber, titanium,titanium alloys, tantalum, chrome cobalt, surgical steel, or any othertotal joint replacement metal and/or ceramic, bony in-growth surface,sintered glass, artificial bone, any porous metal coat, metal meshes andtrabeculations, metal screens, uncemented metal or ceramic surface,other bio-compatible materials, or any combination thereof. The tray 130and overhang portion 131 may further be covered with various coatingssuch as antimicrobial, antithrombogenic, and osteoinductive agents, or acombination thereof. See U.S. Pat. No. 5,866,113 to Hendriks, et al,incorporated herein by reference. These agents may further be carried ina biodegradable carrier material with which the pores of the tray 130and overhang portion 131 may be impregnated. In one preferredembodiment, the tray comprises a metal-backed polyethylene component.

40). The tray 130 and/or the overhang portion 131 may be fixed to thesubtalar joint 90 with poly(methylmethacrylate) bone cement,hydroxyapatite, a ground bone and marrow composition, screws, or acombination thereof, or any other fixation materials common to one ofskill in the art of joint replacement surgery. In the preferredembodiment, the tray 130 and overhang portion 131 are fitted over theMorse taper 115 a of the talo-calcaneal stem 110 and fixed to the talusand calcaneus with screws 133 a and 133 b. In the preferred embodiment,as best seen in FIG. 4, screw 133 a transects talo-calcaneal stem 110 tofurther fix and stabilize the talo-calcaneal stem 110 to the subtalarjoint 90. If desired, the screws can extend anteriorly, posteriorly,medially, laterally and/or at oblique angles, or any combinationthereof. Alternatively, or in combination with other fixation methods,the talo-calcaneal stem 110 may be fixed into the bone cavity with abone cement.

A lower prosthesis body may be attached to the tray 130 and/or aninterlocking device and/or directly to sections of the subtalar joint90. In the preferred embodiment, a plastic convex dome 160, preferablymade of materials such as plastic, ceramic, or metal, is attached toMorse taper 115 a. In this embodiment, the lower prosthesis body 95 ofthe present invention comprises: a talo-calcaneal stem 110 made of anytotal joint material or materials commonly used in the prosthetic arts,including, but not limited to, metals, ceramics, titanium, titaniumalloys, tantalum, chrome cobalt, surgical steel, or any other totaljoint replacement metal and/or ceramic, bony in-growth surface, sinteredglass, artificial bone, any uncemented metal or ceramic surface, or acombination thereof, the stem being desirably located in a cavity formedthrough the talus 100 and calcaneus 105, the stem further comprising aMorse taper 115 a at its upper surface; a tray 130 made of any totaljoint material or materials commonly used in the prosthetic arts,including, but not limited to, metals, ceramics, titanium, titaniumalloys, tantalum, chrome cobalt, surgical steel, or any other totaljoint replacement metal and/or ceramic, bony in-growth surface, sinteredglass, artificial bone, any uncemented metal or ceramic surface, or acombination thereof, with an overhang portion 131, the tray 130 andoverhang portion 131 being fitted over the subtalar joint 90 and theMorse taper 115 a of the bony in-growth stem 110, and fixed to the talus100 and calcaneus 105 with two screws 133 a and 133 b, wherein screw 133a further transects and fixes talo-calcaneal stem 130; and apolyethylene, or other plastic, ceramic, or metal convex dome 160 whichis locked into the Morse taper 115 a.

FIGS. 8 and 9 illustrate side and rear views, respectively, of analternate embodiment of a lower prosthesis body constructed inaccordance with the teachings of the present invention. Lower prosthesisbody 300 comprises a tray 305 and stem 310, which in this embodiment areformed in a single unit. However, it should be understood that thepresent teachings could equally apply to a multi-component prosthesiswhere the stem and tray form separate components. Desirably, as bestseen in FIG. 8, the stem 310 extends downward from the tray 305, formingan angle arelative to the vertical axis—taken relative to thelongitudinal axis of the tray 305 (front to rear of the foot). In apreferred embodiment, the angle α will range from 105° to 205°,dependingupon the size and orientation of the calcaneus as well as the positionof the lower prosthesis body. Moreover, as best seen in FIG. 9, the stemmay form an angle β relative to the vertical axis—taken relative to thetransverse axis of the tray 305 (medial to lateral side of the foot). Ina preferred embodiment, the angle β will range from 155° (on the medialside of the foot) to 240° (on the lateral side of the foot), dependingupon the size and orientation of the calcaneus as well as the positionof the lower prosthesis body. Desirably, the lower portion of the stemof the implant will not extend outside of the calcaneus. Openings 315can be provided, if desired, for screws or other attachment means toattach the implant to the talus and/or calcaneus.

The upper surface of the tray can be designed to fit the particularneeds and walking requirements anticipated by the physician and patient.For example, a low demand surface, such as for an individual of advancedyears having a less-active lifestyle, could comprise a simple smootharc, without the “peaks and valleys” of the talus that run from anteriorto posterior. In addition, a low demand surface may not require adifference in the anterior to posterior talar width, which in an adultmale can be approximately 4 to 5 mm wider in its anterior portion thanits posterior portion. A higher demand surface, for a more activeindividual, may incorporate the trochlea (valley) in the talus as wellas various other anatomical features found on the talus.

The novel ankle replacement system of the present invention may furthercomprise an upper prosthesis body. In one embodiment, the upperprosthesis body 170 comprises a tibial stem 150. The tibial stem 150 maybe made of any total joint material or materials commonly used in theprosthetic arts, including, but not limited to, metals, ceramics,titanium, titanium alloys, tantalum, chrome cobalt, surgical steel, orany other total joint replacement metal and/or ceramic, bony in-growthsurface, sintered glass, artificial bone, any uncemented metal orceramic surface, or a combination thereof. The tibial stem 150 mayfurther be covered with one or more coatings such as antimicrobial,antithrombotic, and osteoinductive agents, or a combination thereof.These agents may further be carried in a biodegradable carrier materialwith which the pores of tibial stem 150 may be impregnated. See U.S.Pat. No. 5,947,893.

The tibial stem 150 may be fixed into the tibia withpoly(methylmethacrylate) bone cement, hydroxyapatite, a ground bonecomposition, screws, or a combination thereof, or any other fixationmaterials common to one of skill in the art of prosthetic surgery. Inthe preferred embodiment, the tibial stem 150 is fixed to the tibia withscrews 125 a and 125 b. If screws are used, they can extend anteriorly,posteriorly, medially, laterally and/or at oblique angles, or anycombination thereof.

The tibial stem 150 may be variable lengths from 2 cm to 30 cm andvariable widths from 6 to 12 mm. In the preferred embodiment, the tibialstem 150 is preferably at least 6 inches in length. Of course, it shouldbe understood that the disclosed tibial stem could be of virtually anylength, depending upon the size of the patient, his or her bonedimensions, and the anticipated future mobility of the patient. Ingeneral, a larger patient, having larger bones, with a high anticipatedmobility (i.e. he or she will be walking/running around quite a bit)would desirably have a longer stem to provide increased stability andbroader distribution of stress to prevent subsidence, loosening, andtibial osteolysis. If desired, the stem can incorporate ananti-rotational feature such as outwardly extending fins—for example,one or more fins, 0.5 to 25 cm long, 1 to 3 mm wide, sharp edges ordull, located along the stem—or a bow to the stem—for example, rangingfrom 1 to 10 degrees bow, anterior or posterior or lateral, or somecombination thereof. Moreover, if desired the surface of the tibial stemcan incorporate irregularities such as wedges or points, desirablyangled towards the knee, which inhibit and/or prevent the tibial stemfrom subsiding. Alternatively, the width of the tibial stem may varyalong the length of the stem, further inhibiting and/or preventingrotation and/or subsidence.

The tip of the tibial stem 150 may additionally have interlockingcomponents, common to those of skill in the art, at its lower surface toallow other components of the upper prosthesis body to lock into thetibial stem. In the preferred embodiment, the tibial stem 150, has aMorse taper 115 b at its lower surface.

An upper prosthesis body may be fixed to the tibial stem and/or aninterlocking device and/or directly to sections of the tibia. In thepreferred embodiment, a concave dome 155, preferably made of a plastic,ceramic, or metal, is attached to the Morse taper 115 b. In thepreferred embodiment, the upper prosthesis body 170 comprises: a tibialstem 150 made of any total joint material or materials commonly used inthe prosthetic arts, including, but not limited to, metals, ceramics,titanium, titanium alloys, tantalum, chrome cobalt, surgical steel, orany other total joint replacement metal and/or ceramic, bony in-growthsurface, sintered glass, artificial bone, any uncemented metal orceramic surface, or a combination thereof, the stem being fixed into thetibia 140 with two screws 125 a and 125 b; a Morse taper 115 b locatedat the lower surface of the tibial stem 150; and a concave dome 155,preferably made of polyethylene, or another plastic, ceramic or metal,locked into the Morse taper 155 b.

In a further embodiment, the upper prosthesis body 170 of the presentinvention may additionally comprise a fibular prosthesis of any varietyknown in the art of joint replacement. In still a further embodiment ofthe present invention, either the lower prosthesis body 95, upperprosthesis body 170, or both, as described above, may be fixed intostrengthened or fortified bone. The bones of the subtalar joint, tibiaor fibula may be strengthened prior to or during fixation of theprosthesis using the methods described in U.S. Pat. No. 5,827,289,incorporated herein by reference. This type of bone strengthening isparticularly suggested for osteoporotic and/or osteopenic patients whowish to have a TAR.

Surgical Procedure

The present invention addresses a novel surgical procedure forperforming TAR which reduces healing time and probability of infection,problems which contribute to the failure rate of currently availableTARs. The novel surgical procedure comprises introducing some and/or allof an ankle prosthesis for TAR through the tibia and/or small incisionsin the foot and/or ankle. The preferred embodiments of the novelsurgical procedure described herein will be described as a method toinstall the preferred embodiment of the TAR system described above. Oneof skill in the art, however, will note that this type of surgicalprocedure, i.e. introducing ankle prostheses into the ankle via anexposure in the upper tibia, may be used to introduce some and/or all ofany feasible prostheses into the ankle region.

In one embodiment of the novel surgical procedure, an exposure 200 ismade at the tibial tubercle with an awl. Once the exposure has beenmade, the exposure may be kept open under distraction, pulling of theskin, or any other method common in the surgical arts. A surgeon canthen introduce various prosthetic parts and surgical instruments throughthe tibia into the ankle joint. Non-invasive visualization of theprocedure can be accomplished through fluoroscopy or real time MRI, aswell as through other means well known to those skilled in the art.Alternatively, or in conjunction with such less-invasive means ofvisualization, open visualization may be used for part and/or all of theprocedure.

In the preferred embodiment, a guide wire is placed through the tibiaand just through the tibial plafond. A tibial rod 200 with reamers isthen pushed down the guide wire. Alternatively, the guide wire andtibial rod may be placed through the tibia simultaneously or a tibialrod may be placed through the tibia without a guide wire. The reamersare preferably 7, 8, 9, or 10 mm wide, depending on the size of thepatient's tibia.

In the preferred embodiment, the tibia and tibial plafond are thenreamed to create an appropriate cavity in the tibia. Bony cuts may thenbe made in the talus 100 and the end of the tibia 140 to create a flatsurface for prosthetic attachment. Alternatively, it is preferable toream the top of the talus 100 and the bottom of the tibia 140 with anarticular reamer 225 fitted over the end of the tibial rod 220, asdepicted in FIG. 6.

In the preferred embodiment, once the surface of the talus 100 has beenflattened, a hole may be drilled through the talus 100 into theposterior section of the calcaneus 105 to form a cavity for insertion ofa talo-calcaneal stem 110 as, for example, depicted in FIG. 1 and FIG.7. Alternatively, the hole may be drilled before the surface of thetalus 100 has been flattened. The hole may be drilled using a talar stemjig, or any other surgical equipment used in the surgical arts. Thedrill bit for the talar stem jig is preferably about 1 mm wider than thewidth of the talo-calcaneal stem 110.

Once the hole through the talus 100 and calcaneus 105 is drilled to formcavity, any easily accessed cartilage from the talo-calcaneal joint maybe scraped. The scraping may be performed with a small angled curet orany other instrument commonly used in the surgical arts. The subtalarjoint 90 can then be fused by passing a talo-calcaneal stem 110 down thecavity. In one embodiment, the cavity may be partially filled with abone cement prior to the installation of the talo-calcaneal stem 110 tohelp fix the talo-calcaneal stem 110 to the subtalar joint 90. In thepreferred embodiment, the stem 110 has a bore hole to allow furtheranchoring of the stem with a screw as described below.

The talo-calcaneal stem 110 preferably comprises a Morse taper 115 a atits upper surface. In the preferred embodiment, once the talo-calcanealstem 110 is installed into the cavity, a tray 130, and a plastic convexdome, preferably made of polyethylene, are placed over and locked intothe Morse taper 115 a. In the preferred embodiment, the tray 130 andoverhang portion 131 of the tray are then anchored or fixed to thesubtalar joint 90. Preferably the tray 130 and overhang 131 are anchoredto the subtalar joint 90 with screws 133 a and 133 b such that screw 133a also passes through the talo-calcaneal stem 110, as best seen in FIG.4, to provide additional anchoring for the talo-calcaneal stem 110.

After the lower prosthesis body 95 of the present invention has beeninstalled, or alternatively, while the lower prosthesis body 95 is beinginstalled or before the lower prosthesis body 95 is installed, an upperprosthesis body 170 may also be installed. In the preferred embodiment,a concave dome 155, preferably made of polyethylene, is placed into theankle joint. A tibial stem 150 is then passed down the tibia to theankle joint. The tibial stem 150 is preferably approximately 1 mm lessin diameter than the size of the largest reamer, and preferablycomprises a Morse taper 115 b at its lower surface.

Once the tibial stem 150 is installed, the concave dome 155 can belocked into Morse taper 115 b. The tibial stem 150 may be fixed into thetibia with bone cement, screws, nails, anchors, or a combinationthereof. In the preferred embodiment, the tibial stem 150 is fixed intothe tibia with screws 125 a and 125 b. Once the lower prosthesis body95, upper prosthesis body 170, or both, have been installed, anyremaining surgical instruments may be removed through the exposure 200and the exposure may sutured closed.

In a further alternative embodiment, a cavity can be formed in thecalcaneus using the teachings of U.S. Pat. No. 5,827,289 to Reiley,either before, during, or after access to the calcaneus has beenaccomplished through the tibia. This cavity can eventually be filledwith material which hardens around some or all of the prosthesis,thereby anchoring the lower prosthesis primarily into the calcaneus. Ifdesired, the prosthesis could incorporate a plurality of rotatableand/or slidable joints, which can allow transverse motion between thetalus and the calcaneus while concurrently allowing relative motionbetween the talus and the tibia, thereby more accurately mimicking thenatural motion of the human foot.

In other embodiments, the upper prosthesis body 170 of the presentinvention may additionally comprise a fibular prosthesis of any varietyknown in the art of joint replacement, which may also be installedthrough exposure 200. In still further embodiments of the presentinvention, either the lower prosthesis body 95, upper prosthesis body170, or both, as described above, may be fixed into strengthened orfortified bone. The bones of the subtalar joint, tibia or fibula may bestrengthened prior to or during fixation of the prosthesis using themethods described in U.S. Pat. No. 5,827,289 to Reiley. This type ofbone strengthening procedure is particularly suggested for osteoporoticpatients who wish to have a TAR.

Surgical Instruments

One novel surgical instrument particularly well suited for use with thedevices and methods of the present invention is a telescoping reamerwhich significantly simplifies the preparation of the ankle joint forreceiving the prosthesis and greatly reduces the amount of traumaexperience by the tissues at the ankle joint. Desirably, the reamer willcomprise a cylindrical shaft having a maximum diameter less than thereamed inner diameter of the tibia, and a length equal to or greaterthan the length of the tibia. At the distal end of the reamer, a reamerfitting, preferably a snap lock or other type of quick-release fitting,may be formed. At the proximal end of the reamer, a drive handle orother device is desirably fitted to provide torsional and axial forcesto the reamer.

Desirably, a reamer head can be attached to the distal end of thereamer. If the reamer head is of a smaller maximum diameter than theinner diameter of the reamed tibia, the reamer head can be passed downthrough the tibia and/or calcaneus, and the lower surfaces of the tibia,for the prosthesis. However, if the reamer head is of equal or greaterdiameter than the inner diameter of the reamed tibia, the reamer headcan be alternatively inserted into the joint region through an incisionmade at or near the joint, and can be attached to the distal end of thereamer which extends through the tibia. In this manner, the reamer headcan be inserted through a very small incision, such as a verticallyextending incision, but can be properly positioned and operated at theend of the reamer. When reaming is completed, the reamer head can bedetached and removed through the same small incision, and the reamerwithdrawn through the reamed tibia.

In a similar manner, the prosthesis could be inserted through the reamedtibia, or could alternatively be inserted through one or more smallerincisions through the ankle and/or foot, and then manipulated usinginstruments and/or visualization devices passing through the reamedtibia. In fact, if desired, the prosthesis could be formed of a seriesof smaller components which are ultimately assembled within the jointcavity.

Another novel surgical instrument for use with the devices and methodsof the present invention is a talo-calcaneal jig 600, best shown inFIGS. 7, 7A and 7B. FIG. 7 depicts a tibia 670 which is slightlydistracted from a fibula 665, a talus 650 and a calcaneus 660 of a humanankle. A tibial stem 680 extends through at least a portion of the tibia670, and is secured to the tibia by screws 690. The fibula 665 isdistracted from the tibia 670 and the talus 650 and calcaneus 660. A jig600 is positioned on top of the talus 650. The jig 600 desirablycomprises a base plate 610 and extension piece 620, with a passage 630extending therethrough. The passage 630 is desirably sized toaccommodate a drill (not shown) for creating a void 640 within the talus650 and calcaneus 660 for implantation of the prosthesis. Desirably, thejig 600 will fit over the upper surface of the talus, and will guide thedrill (not shown) in creating a void 640 of desired shape and size intothe talus 650 and calcaneus 660. Once the void is created, the jig 600can be removed and the prosthesis (not shown) inserted into the void640.

It should be understood that the devices and methods of the presentinvention could be used as an index (initial) total ankle replacement,as well as a revision ankle replacement. If used as a revision device,only a portion of the disclosed methods and devices may be necessary inconjunction with such a procedure.

Other embodiments and uses of the inventions described herein will beapparent to those skilled in the art from consideration of thespecification and practice of the inventions disclosed. All documentsreferenced. herein are specifically and entirely incorporated byreference. The specification should be considered exemplary only withthe true scope and spirit of the invention indicated by the followingclaims. As will be easily understood by those of ordinary skill in theart, variations and modifications of each of the disclosed embodimentscan be easily made within the scope of this invention as defined by thefollowing claims.

1. An ankle prosthesis configured to be attached to a calcaneus and atalus, the talus having a flat surface formed at an upper portion, theankle prosthesis comprising: a lower prosthesis body including: atalo-calcaneal stem sized and configured to be disposed within a cavityformed through the talus and the calcaneus, the talo-calcaneal stemhaving an upper end including a Morse taper, said talo-calcaneal stemhaving a length sufficient to extend across a joint between the talusand calcaneus while the lower end is disposed within a distal part ofthe calcaneus and the upper end is disposed within a top of the talus; atray having a first portion configured to be disposed over thetalo-calcaneal stem and fixed to the flat surface formed on the talus,said tray including an overhang portion extending from the first portionat angle, the overhang portion sized and arranged to extend outward ofthe talus and to overlap a portion of the calcaneus, said overhangportion including a region attachable to the calcaneus; and a generallyconvex dome configured to lock to the Morse taper of the talo-calcanealstem; and an upper prosthesis body including: a tibial stem configuredto be disposed in a tibia, the tibial stem including a Morse taper at alower surface; and a generally concave dome configured to lock to theMorse taper of the tibial stem.
 2. The ankle prosthesis of claim 1wherein a length of the talo-calcaneal stem is from about 65 mm to about12 cm.
 3. The ankle prosthesis of claim 1 wherein a width thetalo-calcaneal stem is from about 4 mm to about 14 mm.
 4. The ankleprosthesis of claim 1 wherein a length of the tibial stem is from about2 cm to about 30 cm.
 5. The ankle prosthesis of claim 1 wherein a widthof the tibial stem is from about 6 mm to about 12 mm.
 6. The ankleprosthesis of claim 1 wherein said generally convex dome includes ananterior section and a posterior section, said anterior section beingmore than 1 mm wider than said posterior section.
 7. The anklereplacement prosthesis of claim 6 wherein said anterior section isapproximately 3 mm wider than said posterior section.
 8. The ankleprosthesis of claim 1 wherein said generally concave dome of the upperprosthesis body is configured to articulate with said generally convexdome of the lower prosthesis body.
 9. The ankle prosthesis of claim 1wherein said generally convex dome includes a trochlea.
 10. An ankleprosthesis, comprising: a tray sized and configured to be fixed to aflat surface formed at an upper portion of a talus; a talo-calcanealstem having a length sufficient to (i) be disposed within a top of thetalus in a cavity formed through the talus and a calcaneus, and (ii) bedisposed within a distal part of the calcaneus while extending across ajoint between the talus and calcaneus, said talo-calcaneal stemincluding a Morse taper at an upper-talar end; and a generally convexdome locked to the taper of the talo-calcaneal stem.
 11. The ankleprosthesis of claim 10 wherein said tray includes an overhang portionsized and arranged to extend from the talus and overlap a part of thecalcaneus.
 12. The ankle prosthesis of claim 11 wherein a length of thetibial stem is from about 2 cm to about 30 cm.
 13. The ankle prosthesisof claim 11 wherein a width of the tibial stem is from about 6 mm toabout 12 mm.
 14. The ankle prosthesis of claim 10 wherein said tray andsaid talo-calcaneal stem are monolithic.
 15. The ankle prosthesis ofclaim 10 further comprising: a tibial stem configured to be disposed ina tibia, said tibial stem including a Morse taper at a lower surface;and a generally concave dome configured to lock to the taper of thetibial stem.
 16. The ankle prosthesis of claim 10 wherein a length ofthe talo-calcaneal stem is from about 65 mm to about 12 cm.
 17. Theankle prosthesis of claim 10 wherein a width of the talo-calcaneal stemis from about 4 mm to about 14 mm.
 18. The ankle prosthesis of claim 10wherein said generally convex dome includes a trochlea.